CN113960460A

CN113960460A - Method for diagnosing the operating state of an electrical switching device and electrical switching device

Info

Publication number: CN113960460A
Application number: CN202110783156.1A
Authority: CN
Inventors: S.德尔巴尔; R.奥尔班; S.福利克
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 2020-07-20
Filing date: 2021-07-12
Publication date: 2022-01-21
Also published as: FR3112649A1; EP3944278A1; FR3112649B1; EP3944278B1; US20220020547A1

Abstract

A method for diagnosing the operating state of a switching device that includes separable contacts driven by an electromagnetic actuator that includes a coil connected to an electronic control device, and a sensor that measures the coil voltage and coil amperage. The method comprises the following steps: a) -receiving (102), by means of an electronic control device, a command to open the switching device; b) controlling (104) the electromagnetic actuator to open; c) measuring and recording (106) coil voltage and coil current values; d) calculating and recording (112) the magnetic flux values through the coil by integrating the recorded values of the coil current and the coil voltage and the resistance and inductance values of the coil; e) the position of the core of the electromagnetic actuator is evaluated and recorded (114) according to a data table defining a bijective relationship between the core position, the magnetic flux and the coil current.

Description

Method for diagnosing the operating state of an electrical switching device and electrical switching device

Technical Field

The present invention relates to a method for diagnosing the operating state of an electrical switching device and to an electrical switching device for implementing such a method.

The invention more particularly relates to an electrical contactor.

Background

Such an electrical switching apparatus comprises an electromagnetic actuator having a coil and is configured to switch between an open state and a closed state, for example in order to control the supply of electrical power to an electrical load. Typically, the electrical contacts comprise a fixed contact and a movable contact, the latter being attached to a movable part of the actuator, which moves under the action of a magnetic field generated by the coil when a suitable current flows through the coil. In order to ensure a sufficient contact pressure between the electrical contacts, the movable part of the actuator moves over a distance, called over travel, between the moment when the movable contact is in contact with the fixed contact and the moment when the actuator reaches its stable closed position. This over travel corresponds to contact compression.

During each switching cycle, the contactor is subject to wear under the action of various factors; for example, the electrical contacts wear under the action of the arc generated when the electrical contacts open, the wear of the contactor manifests itself as a loss of compression of the contacts.

It is desirable to be able to automatically estimate the wear level of a contactor as it operates so as to be able to provide proper maintenance and/or detect the occurrence of faults during the useful life of the contactor.

It is known to incorporate position sensors into electromagnetic actuators in order to directly measure the movement of the movable part of the actuator and deduce therefrom the contact compression. However, the use of additional sensors incurs additional costs and it is not always possible to integrate new sensors into existing contactors.

EP-2584575-a1 describes a method of diagnosing wear based on a measurement of the time between peaks of current flowing through the actuator coil during the off phase. This diagnostic method only allows to determine the time at which the movement of the core starts and the time at which the movement ends. One drawback of this method is therefore that it does not allow to determine the exact position of the core during the breaking phase. This makes it more difficult to obtain reliable information about the state of the contacts and thus about the state of wear of the contactor.

The present invention more specifically addresses these problems by providing a more accurate diagnostic method.

Disclosure of Invention

To this end, the invention relates to a method for diagnosing the operating state of an electrical switching device. An electrical switching apparatus is configured to be coupled to an electrical conductor and includes:

separable contacts associated with the electrical conductors and driven by an electromagnetic actuator comprising a coil connected to an electronic control device configured to apply a coil command voltage across terminals of the coil,

-a sensor configured to measure the magnitude of the coil voltage and the coil current flowing through the coil.

According to the invention, the method comprises the following steps:

-receiving a command to open the switching device, the switching device being initially in the closed state, the opening command being received by the electronic control means;

-commanding, by the electronic control means, the opening of the electromagnetic actuator upon reception of the opening command;

-measuring and storing values of the coil voltage and the coil current when the switching device is switched to the off-state;

-calculating and storing the magnetic flux values crossing the coil by integration of the stored values of coil current and coil voltage and of the values of resistance and inductance of the coil previously stored in the electronic control means;

-evaluating and storing the position of the core of the electromagnetic actuator according to the characteristics of a data table of the electromagnetic actuator, stored in advance in the electronic control means and defining a bijective relationship between the core position, the magnetic flux and the coil current, on the basis of the stored values of the magnetic flux and the coil current.

By means of the invention, the magnetic flux is calculated throughout the off-phase based on measurements of the coil voltage and the coil current. From which a position value of the movable core is derived from the data table, which value is related to the core position, the magnetic flux and the coil current bijection. Therefore, in the disconnection stage, the position change of the movable core is automatically and accurately determined, and it is not necessary to install a specific new sensor, such as a position sensor.

According to some advantageous but not mandatory aspects of the invention, such diagnostic methods may incorporate one or more of the following features, alone or in any technically allowable combination:

the step of calculating the magnetic flux comprises an initial sub-step, called self-correction sub-step, followed by a calculation sub-step, the self-correction sub-step comprising: in the case of a coil current higher than a low threshold value, itself strictly higher than a current called "locked rotor" current below which the movable core is repelled by the return member of the electromagnetic actuator to the open position, an initial value of the magnetic flux, called "initial flux", is evaluated and stored, so that when the coil current drops below the locked rotor current, the value of the initial flux is taken into account by the calculation of the integral of the magnetic flux in the calculation phase;

the electronic control means are configured to vary the coil voltage when the switching device is in the closed state, so that the coil current varies between a low threshold and a high threshold strictly higher than the low threshold, and, after receiving the opening command, to command the opening of the electromagnetic actuator when the coil current is higher than or equal to 80%, preferably higher than 95%, more preferably higher than 98%, of the high threshold;

-periodically varying the coil voltage, for example by chopping, the coil current also periodically varying between a low threshold and a high threshold, and, after receiving the opening command, the electronic control device commands the opening of the electromagnetic actuator at the end of a predetermined duration after receiving the opening command, the predetermined duration being equal to one period of the coil voltage;

the electronic control device is configured to calculate a time, called "release" time, equal to the time elapsed between the time at which the electronic control device commands the opening of the electromagnetic actuator and the time at which the electromagnetic actuator reaches the open position;

-the method comprises the steps of: calculating a movement velocity profile of the switching device and an acceleration profile of the switching device by deriving a position value of the switching device with respect to time, which is stored in the electronic control means, and storing the velocity profile and the acceleration profile of the switching device in the electronic control means;

the method comprises the step of calculating a speed value, called "detachment" speed, equal to the speed of movement of the core when it is in a position, called "maximum overtravel" position, corresponding to the movement of the core from its closed position to its open position, substantially equal to 2 mm; and

-the method comprises the steps of: in the off phase of the switchgear, a local minimum of the core speed is detected between the start of the movement of the core and the moment when the core reaches the abutment of the off position.

The invention also relates to an electrical switching device for implementing the above diagnostic method, comprising:

-separable contacts moved between open and closed positions by an electromagnetic actuator comprising a coil and a movable core attached to the separable contacts, the switching device having a structure to limit eddy current generation;

-a command circuit for controlling the voltage between the coil terminals, called "coil voltage", comprising a device called "release" device which can be selectively activated to drop the current flowing through the coil, called "coil current", the coil voltage and the release device being activated or deactivated according to the state of the command circuit;

-sensors for measuring coil current and coil voltage;

-electronic control means configured to receive commands to open and close the switching device, to receive measurements of the coil current and the coil voltage, and to control the state of the command circuit;

wherein the switching device is configured to implement a diagnostic method comprising the steps of:

a) receiving a command to open the switching device;

b) commanding the electromagnetic actuator to open;

c) measuring and storing values of coil voltage and coil current;

d) calculating and storing a magnetic flux value passing through the coil by integrating the stored values of the coil current and the coil voltage and a coil resistance and an inductance value stored in advance in the electronic control device;

e) the position of the core is evaluated and stored on the basis of the characteristics of a data table of the electromagnetic actuator, which is stored in advance in the electronic device and defines the bijective relationship between the core position, the magnetic flux and the coil current.

The switch device has the same advantages as described above in relation to the diagnostic method of the invention.

Drawings

The invention will be better understood and other advantages will become more apparent from the following description of an embodiment of a method for diagnosing the operating state of a contactor and a contactor configured to implement such a method, given by way of example only and with reference to the accompanying drawings, in which:

fig. 1 is a schematic diagram of an electrical switching apparatus including an electromagnetic actuator in accordance with an embodiment of the present invention;

fig. 2 is a schematic diagram of an example of a command circuit for controlling an electromagnetic actuator of the switchgear of fig. 1;

FIG. 3 is a graph of commanded current for the electromagnetic actuator of FIG. 2 during various stages of operation;

FIG. 4 is a graph illustrating the change in command current for the electromagnetic actuator of FIG. 2 in two phases of operation in two different states;

FIG. 5 is a graph showing the change in command current and magnetic flux measured by the electromagnetic actuator of FIG. 2 during a phase of opening the actuator;

FIG. 6 is a graph illustrating one of the steps of the diagnostic method;

FIG. 7 is a graph illustrating results of a method for diagnosing characteristics of the switchgear of FIG. 1, in accordance with an embodiment of the present invention;

FIG. 8 is a graph illustrating the sensitivity of the magnetic flux of the electromagnetic actuator of FIG. 2 as a function of command current for the electromagnetic actuator;

FIG. 9 is a chart illustrating steps of a method for diagnosing characteristics of the switchgear of FIG. 1 in accordance with an embodiment of the present invention;

fig. 10 is a graph illustrating one example of the result of the method according to the invention in the opening phase of the switchgear of fig. 1;

fig. 11 is a graph illustrating another example of the result of the method according to the invention in the opening phase of the switchgear of fig. 1; and

fig. 12 is a graph illustrating another example of the result of the method according to the invention in the off phase of the switching installation of fig. 1.

Detailed Description

Fig. 1 shows a contactor 1. The contactor 1 is an example of an electrical switching apparatus intended to control the supply of electrical power from an electrical power source to an electrical load 23. The power supply is not shown to simplify the drawing. The power source is for example the main grid, and the electrical load 23 is for example an electric motor which it is desired to control and/or protect through the contactor 1. The contact 1 is normally accommodated in a housing, here indicated by a dashed rectangle. The contactor 1 is configured to be coupled on the one hand to an upstream electrical conductor 20 connected to an electrical power source and on the other hand to a downstream line 22 connected to an electrical load 23. When the contactor 1 lets through current and the electrical load 23 is supplied with power, the contactor 1 is in a state referred to as a "closed" state, and when the contactor 1 blocks power to the electrical load, the contactor 1 is in a state referred to as an "open" state.

The electrical conductor 20 and the downstream line 22 comprise the same number of phases. When the power source is multi-phase, electrical conductor 20 and downstream line 22, each comprising mutually insulated conductors, have as many conductors as each other, each conductor of downstream line 22 being associated with a respective wire of upstream electrical conductor 20. Regardless of the number of phases, the contactor 1 is configured to jointly interrupt or let through the current in each phase.

In the illustrated example, upstream electrical conductor 20 is three-phase. In fig. 1, a single wire of the electrical conductor 20 is shown, which is labeled 201. Only the conductor of the power line 22 associated with the conductor 201 is shown, this conductor of the power line 22 being referenced 221.

The remaining description will be given with reference to

conductors

201 and 221 associated with the same phase of the supply current, but it should be understood that the description may be switched to other phases of the supply current.

For each phase, the contactor 1 comprises a movable contact 24 placed on a movable rod 26 and a fixed contact 28 attached to the upstream and

downstream conductors

20, 22, respectively. Each movable and fixed

contact

24, 28 comprises a contact pad 29, here made of metal, and preferably made of silver alloy or any equivalent material.

The movable rod 26 is movable between a closed position, in which the movable contact 24 is electrically connected to the fixed contact 28 and electrical power can flow through the movable rod 26 of the upstream electrical conductor 20 to the downstream line 22, and an open position, in which the movable contact 24 is separated from the fixed contact 28.

When the movable lever 26 is in the closed position, the contactor 1 is in the closed state, and when the lever 26 is in the open position, the contactor 1 is in the open state. The process from the open state to the closed state is the closing phase of the contactor 1, and the process from the closed state to the open state is the opening phase of the contactor 1.

In fact, during each cycle comprising a closing and an opening phase, the contact pads 29 wear, for example under the action of an electric arc generated when the contactor opens, or even due to micro-welding, causing the material to tear off. The result of this loss of material is that the thickness of the contact pad 29 decreases over the life of the contactor 1, which increases the amplitude of the movement of the rod 26 during the opening and closing phases. To solve this problem, the contactor 1 comprises a mechanism 290, schematically represented in fig. 1 by a spring, which mechanism 290 is attached to the rod 26 and allows the fixed and

movable contacts

28, 24 to maintain electrical contact with a sufficient contact pressure.

When the thickness of the contact pad 29 is insufficient or the surface finish of the contact pad 29 is poor, the risk of malfunction of the contactor 1 increases, suggesting replacement of the contactor 1; it is for these reasons that the diagnosis of the state of compression of the contacts of the contactor 1 allows to evaluate the progress of the degradation of the contactor 1.

The movable rod 26 is driven by an electromagnetic actuator 30 comprising a command electromagnet having a coil 32, a core 34 attached to the movable rod 26 and a return member 36, such as a spring or equivalent. The coil 32 is configured to generate a magnetic field when it is energized by a commanded current to cause the core 34 (and thus the movable rod 26) to move. The movement of the core 34 between the open and closed positions is represented by the double arrow F34. In other words, the movable contacts 24 and the associated fixed contacts 28 together form separable contacts that are associated with the electrical conductors 20 and are moved between the open and closed positions by the electromagnetic actuator 30, the electromagnetic actuator 30 including the coil 32 and the movable core 34 attached to the separable contacts.

In fig. 1, the contactor 1 is shown in an intermediate configuration between the stable open and closed states of the contactor 1, in which the fixed contacts 28 and the movable contacts 24 are electrically connected, while the core 34 is not in abutment in the closed position. The mechanism 290 allows the overtravel of the core 34 between the moment when the fixed contacts 28 are in contact with the movable contacts 24 and the moment when the actuator 30 is in its stable closed position. This over travel corresponds to contact compression, indicated as E in fig. 1.

The electromagnetic actuator 30 is controlled by a power supply circuit 38, the power supply circuit 38 itself being controlled by an electronic control device 40. The coil 32 is thus connected to the electronic control device 40.

According to some embodiments, the electronic control device 40 includes a Central Processing Unit (CPU), such as a programmable microcontroller, microprocessor, or the like, and a computer memory forming a storage medium for computer-readable data.

According to some examples, the memory is a ROM memory, a RAM memory, or an EEPROM or flash non-volatile memory, or the like. The memory comprises executable instructions and/or computer code for ensuring the operation of the control device 40 according to one or more embodiments described below when executed by the central processing unit.

As a variant, the electronic control means 40 may comprise a Digital Signal Processor (DSP), or a Field Programmable Gate Array (FPGA), or an Application Specific Integrated Circuit (ASIC), or any equivalent element.

The electronic control means 40 are themselves connected to a power rail 42 and comprise an interface 44, the interface 44 being configured to receive from a user a command to open or close the shape device 1. The electronic control device 40 is shown here as being integrated into the contactor 1. As a variant, the control device 40 is remote, i.e. it is not integrated in the same housing as the electromagnetic actuator 30.

The power supply rail 42 has a preferably stable direct voltage and is intended to supply the electronic control device 40 and the supply circuit 38. The interface 44 is here represented by a command electrode. For example, a command voltage may be applied across the command electrodes. Optionally, the interface 44 comprises a wireless communication device.

In certain embodiments, the contactor 1 further comprises a current sensor 46 configured to measure the current flowing through each phase of the upstream line 20, or in other words, the current flowing through each wire 201 of the upstream line 20. In other embodiments, the current sensor and the electronic control device are integrated into a housing separate from the contactor 1.

When the coil 32 is supplied with power delivered by the power rail 42, an excitation current passes through the coil 32, which generates an electromagnetic force that tends to attract the core 34 and the stem 26 from the open position to the closed position. A return member 36, here represented by a spring, exerts a return force opposing the attractive force of the electromagnet.

Coil current I_BOBDefined as the excitation current flowing through the coil 32.

Starting current I_DDefined as the coil current I_BOBWhen the actuator 1 is in the off-state, upon the coil current I_BOBUp to a starting current I_DIn the above, the actuator 1 is allowed to move to the closed state.

Locked rotor current I_SDefined as the coil current I_BOBWhen the actuator 1 is in the closed state, upon the coil current I_BOBDown to locked-rotor current I_SThe actuator 1 is then moved to the off state.

Thus, when the actuator 1 is in the off-state, it is assumed that the coil current I_BOBKept below the starting current I_DThe movable core 34 is repelled to the open position by the return member 36 of the actuator 30 and the contactor 1 is held in the open state. If the coil current I_BOBIncreased above the starting current I_DThe core 34 moves from its open position to its closed position. This situation corresponds to the closing phase of the contactor 1.

In contrast, when the actuator 1 is in the closed state, the coil current I is_BOBHoldingHigher than locked rotor current I_SIn the case of (1), the contactor 1 is kept in a closed state. If the coil current I_BOBReduced to locked-rotor current I_SThereafter, the electromagnetic force of coil 32 is reduced below the return force of member 36 and mechanism 290; the core 34 is then repelled from its closed position to its open position by the action of the return member 36 and the mechanism 290. This situation corresponds to the opening phase of the contactor 1.

In general, the starting current I_DIs higher than the locked-rotor current I_S. During the design of the actuator 1, the start-up and stall currents I are adjusted, in particular by adjusting the characteristics of the coil 32 or the return force of the member 36 and the mechanism 290_D、I_SThe value of (c).

Fig. 2 schematically illustrates an exemplary embodiment of the power supply circuit 38. The architecture of the power supply circuit 38 is non-limiting and other arrangements of the various components of the power supply circuit 38 are possible and other electrical or electronic components may actually be used to perform the same function.

The power supply circuit 38 preferably includes a measurement circuit 50, shown as a dashed rectangle on the left, configured to measure the value of the voltage between the power rail 42 and the electrical ground GND of the power supply circuit 38.

For example, the measurement circuit 50 includes two resistors R1 and R2 connected in series with a diode Dt between the power rail 42 and the electrical ground GND. The first measurement point located between the resistors R1 and R2 allows to collect a first measurement voltage V1 representative of the voltage present between the power rail 42 and the electrical ground GND. Due to the voltage existing between the rail 42 and the ground GND and the coil voltage U_BOBIn connection therewith, the measuring circuit 50 is thus configured to measure the coil voltage U_BOBAn extended example of the sensor of (1).

The power supply circuit 38 includes a command circuit 51, which includes the coil 32. A diode D1 may be placed on power rail 42 between command circuit 51 and measurement circuit 50 to prevent current from returning to measurement circuit 50. Diodes D1 and Dt are preferably of the same type.

The instruction circuit 51 is shown here in a configuration referred to as a "release" configuration, which is described in more detail further in this specification.

The command circuit 51 includes a power supply terminal 52 connected to the power supply rail 42. The coil 32 includes two

terminals

54 and 56. Thus, the measurement of the voltage between

terminals

54 and 56 allows the measurement to be represented as U_BOBThe coil voltage of (1).

Terminal 54 is connected to ground GND through a switch t1 called the "release" switch. In many embodiments, a resistor Rsh, referred to as a shunt resistor, is connected in series with the release switch T1 to collect a signal representative of the current flowing through the coil 32 (or in other words, representative of the coil current I)_BOB) And a second measurement voltage V2. In the example shown, a shunt resistor Rsh is connected between the release switch T1 and ground GND. Resistor Rsh is configured to measure coil current I flowing through coil 32_BOBAn example of a sensor of size (d).

The terminal 56 is connected on the one hand to the terminal 52 through a power switch T2 and on the other hand to ground GND through a diode called "flyback" diode Drl. The flyback diode Drl has a blocking direction oriented toward the terminal 56.

The switches T1 and T2 are switches controlled by command signals from the electronic control device 40. In other words, the electronic control device 40 is configured to control the state of the instruction circuit 51.

According to an example of some embodiments, the switches T1 and T2 are semiconductor power switches, such as MOSFETs, or thyristors, or Insulated Gate Bipolar Transistors (IGBTs), or any other equivalent device.

The command circuit 51 comprises a "release" device Dz, here in the form of a zener diode connected in parallel to the release switch T1. Thus, when the release switch T1 is opened, the coil current I_BOBThrough the release device Dz, and when the release switch T1 is closed, the release device Dz is shorted and no current passes through the release device Dz. The release device Dz is thus selectively activatable to let the coil current I_BOBAnd (4) descending.

In the context of the present invention, the characteristic quantities of the components of the supply circuit 38 are considered to be known. In particular, the coil 32 has the value denoted R_BOBIs expressed as L_BOBThe inductance of (2). Resistance R_BOBAnd an inductance L_BOBDepending on, among other things, the geometry of the coil 32, the materials used, the temperature, etc. Therefore, the resistance R is considered to be_BOBAnd an inductance L_BOBThe value of (c) is known.

Fig. 3 shows a graph 58 which shows the coil current I flowing through the coil 32 in the respective successive operating phases of the contactor 1 in the case of a switching of the contactor into the closed state and then back into the open state_BOBThese phases are denoted as P1, P2, P3 and P4 as a function of time (t).

Phase P1 is the initial phase during which the contactor 1 is stable in the open state, i.e. the coil current I_BOBNot exceeding the starting current I_D. In FIG. 3, the coil current I_BOBContaining

transient peaks

60 and 62 below the start-up current I_DAnd in connection with the operations for testing the contactor 1, these test operations are not described in detail in this specification.

After the contactor 1 receives the closing command, the phase P2 corresponds to the closing phase. When the electronic control device 40 is at time t₀Phase P2 begins when a close command is received via interface 44.

The electronic control device 40 is configured to apply a command coil voltage U to the terminals of the coil 32_BOB. For example, the control device 40 then commands the release switch T1 and the power switch T2 to close. Coil voltage U_BOBAnd thus equals the voltage delivered by the power rail 42 minus the voltage across the terminals of the shunt resistor Rsh. Initially zero coil current I_BOBThen at time t₁Increase to exceed the starting current I_DFrom this time, the core 34 begins to move from its open position to its closed position.

Next, in a closing phase P2, the movable contact 26 abuts against the fixed contact 28; the contactor 1 is then in a closed state. The core 34 continues to move until it comes into contact with the fixed part 30 of the magnetic circuit, which corresponds to an over travel of the compression electrical contact.

More generally, when the power supply comprises a plurality of electrical phases, the pads 29 associated with each electrical phase do not all have the same wear, or in other words, do not all have the same compression. The exact time that each electrical phase is closed varies from electrical phase to electrical phase.

At the final stage 64 of the closing stage P2, the transition effect has ended and the coil current I_BOBExhibits a plateau value equal to the coil voltage U_BOBDivided by the coil resistance R_BOBAnd strictly higher than the locked-rotor current I_S. Then, the contactor 1 is stably in the closed state.

In phase 64, the coil 32 consumes electrical energy, in particular by joule heating, the electrical energy consumed by the coil 32 by joule heating being equal to R_BOB×(I_BOB)2. If the coil current I_BOBMaintained at a locked-rotor current I_SAbove, the contactor 1 is kept in a closed state. Therefore, as long as the coil current I_BOBKept above locked-rotor current I_SIt is possible to reduce the coil current I_BOBTo reduce the power consumption of the coil 32 while stably maintaining the contactor 1 in the closed state.

This is for example done by varying the coil voltage U_BOBIs implemented so as to reduce the coil current I as much as possible_BOBWhile keeping it at the locked-rotor current I_SThe above. This situation corresponds to the hold phase P3.

In the example shown, the coil voltage U_BOBIs achieved by alternately opening and closing the power switch T2, which produces a periodic signal, with a square wave profile of frequency F3, against the coil voltage U_BOBChopping is performed.

In the hold phase P3, the release switch T1 remains closed when the power switch T2 is open. The command circuit 51 is then in a mode referred to as "flyback" mode. The command circuit 51 is limited to the coil 32 connected to the flyback diode Drl and the shunt resistor Rsh. Coil current I_BOBSo that the electric energy is reduced mainly by the resistance R of the coil 32_BOBAnd (6) dissipating. Then, at the coil current I_BOBReduced to locked-rotor current I_SThe power switch T2 is closed before and the coil current I_BOBAnd again increased.

As a result, the coil current I_BOBTo be equal to the coil voltage U_BOBOf frequency F3, here a coilCurrent I_BOBHaving a sawtooth profile, at a current strictly above the locked-rotor current I_SLow threshold value of₁And above a low threshold I₁High threshold value of₂To change between. Low threshold value I₁E.g. selected to be specific to the locked-rotor current I_SThe height is 5 percent. High threshold value I₂In particular on the characteristics of the coil 32, e.g. the coil resistance R_BOBAnd a coil inductance L_BOB。

Coil current I_BOBCauses mechanical vibrations of the electromagnetic actuator 30. To prevent such vibrations from generating noise perceptible to the human ear, the frequency F3 is advantageously chosen to be below 100Hz or above 25 kHz. In the example shown, the frequency F3 is 100 Hz.

The opening phase P4 begins when the electronic control unit 40 receives an opening command, at time t₂。

The electronic control device 40 commands the opening of the electromagnetic actuator 30, which is achieved here by opening the power switch T2 and opening the release switch T1, so as to cause the voltage across the terminals of the coil 32 to drop. Coil current I_BOBAnd then through flyback diode Dr1, coil 32, flyback device Dz, and shunt resistor Rsh. The control circuit 51 is then in a mode called "release" mode, in which the coil current I_BOBFaster than in flyback mode.

When the coil current I_BOBDown to locked-rotor current I_SIn the following, the return member 36 and the mechanism 290 push the movable contacts 24 from their closed position to their open position.

Once the transient induction effect is over, the coil current I_BOBZero, the contactor 1 is again stably in the open state.

FIG. 4 shows a graph 65 illustrating the coil current I flowing through the coil 32 during the transition from the hold phase P3 to the off phase P4_BOBAs a function of time t. Curve 65A (bold line) shows the coil current I when the electronic control device 40 commands the opening of the contactor 1 according to an advantageous opening strategy detailed below_BOBA change in (c). The curve 65B (thin line) shows when the electronic control device 40 commands the opening of the contactor 1 without any particular strategyCoil current I_BOBAs is the case in the prior art.

As described above, during the hold-in phase P2, the coil current I_BOBAt low and high thresholds I₁、I₂Periodically changing in between. The curves 64A and 65B overlap during the hold phase P3.

In the prior art, when at time t₂Upon receiving the off command, the control device 40 immediately instructs the switches T1 and T2 to turn off. Coil current I_BOBThe decrease starts immediately, which corresponds to curve 65B.

Advantageously, in the context of the present invention, when the coil current I_BOBAs high as possible, the control device 40 commands the contactor 1 to open. "as high as possible" means here that the current I is_BOBHigher than or equal to a high threshold I₂Preferably higher than 95%, more preferably higher than 98%.

The time at which the electronic control device 40 commands the opening of the contactor 1 defines the time t₂', which is at time t₂And then.

In order not to delay time t2' excessively, electronic control unit 40 commands electromagnetic actuator 30 to open at the latest at the end of a predetermined duration after receiving the switch-off command, the predetermined duration being equal to coil voltage U_BOBOne period of (a). In other words, at time t₂After receiving the opening command, electronic control unit 40 preferably commands electromagnetic actuator 30 at a first high threshold peak value I₂And (5) disconnecting.

In the example shown, in the hold phase P3, the coil current I_BOBVarying at a frequency F3 of 100 Hz. Thus, two high threshold peaks I₂The time interval between is equal to 10 milliseconds. Thus, time t₂And t₂The offset between' is at most 10ms, which corresponds to half a period of the 50Hz supply current. Such an offset is acceptable in view of the operational limits of the contactor 1.

Locked rotor time t₂"is also defined as the coil current I_BOBAt time t₂' thereafter falling below the locked-rotor current I for the first time_STime of (d). Finally, time t₃Defined as the coil current I_BOBTime to stabilize to zero. Thus, the core 34 is at time t₂' and t₂Is held stationary and at time t₂"then start moving.

The electric and electromagnetic quantities of the coil 32 will now be described.

When the coil current I_BOBA magnetic flux phi is generated when flowing through the coil 32. The value of the magnetic flux phi depends inter alia on the coil current I_BOBAnd the position of the movable core 34.

For example, the value of the magnetic flux φ and the coil voltage U_BOBAnd coil current I_BOBIs related by the following equation, expressed by the following equation 1:

where N is the number of turns of the coil 32 and phi is the magnetic flux through each turn of the coil 32.

The position x is defined as the position of the movable core 34 relative to the coil 32. In many embodiments, the movable core 34 may translate relative to the coil 32 along a movement axis. Then, a position x is defined along the movement axis. Conventionally, when the contactor 1 is in the open state, the position x is zero. The position of the movable contacts 24 is therefore correlated to this position x for each electrical phase of the contactor 1. By extension, this position x also represents the position of the electromagnetic actuator 30 or the contactor 1.

By deriving φ in equation 1, the general equation 2 describing the amount of electromagnetism in the actuator 1 is obtained:

last item of the above

Containing eddy currents, denoted as i_f。

In the context of the present invention, the contactor 1 has limitationsVortex i_fThe resulting structure, which allows the last term of equation 2 to be ignored. According to some non-limiting examples, the contactor 1 has a laminated structure based on sheets, which is made by stacking cut sheets and has a very low electrical conductivity along the stacking axis of the sheets, in particular because of the discontinuity of the edges of the sheets. The resulting low overall conductivity is responsible for the small amount of eddy currents generated by such a contactor 1.

Vortex i_fA diagram of this reduced influence is shown in fig. 5, which shows a diagram illustrating the coil current I in the opening phase of the contactor 1_BOBAnd a plot 66 of the change in magnetic flux. Vortex i_fIs shown in the magnetic flux phi and the coil current I_BOBWithout phase shift therebetween, at the same time t₃All reach zero value.

Since the eddy currents are neglected, the magnetic circuit has a reluctance Rel, i.e. on the one hand, depending on the position x of the movable core 34 and the coil current I_BOBOn the other hand, by the following relationship Rel (x, I)_BOB)·φ＝N·I_BOBWith magnetic flux phi and coil current I_BOBAnd (4) correlating.

In other words, the magnetic flux φ is the position x and the coil current I_BOBThe magnetic flux phi may be expressed in the form of an analytical relationship, or indeed in order to obtain a high precision, by means of a two-dimensional response surface generated by means for simulating the magnetic circuit of the contactor 1.

In most cases, the surface phi ═ f (x, I)_BOB) Having a bijective character, i.e. for a given coil current I_BOBThe given value of position x corresponds to a single value of magnetic flux phi. This allows the reconstruction of the inverse x-g (phi, I)_BOB) Which gives the value of the position x as the magnetic flux phi and the coil current I_BOBAs a function of (c).

The surface phi ═ f (x, I)_BOB) Or its inverse x ═ g (phi, I)_BOB) Stored in the memory of the electronic control device 40, for example in the form of a data table characteristic of the electromagnetic actuator 30, which defines the position x of the core 34, the coil magnetic flux phi and the coil current I_BOBA bijective relationship between.

The magnetic flux phi is also given by the integral of equation 1 with respect to time. The following equation 3 is thus obtained:

wherein at the beginning of the integration interval, U_BOBAnd I_BOBIs measured, N, dt and R_BOBIs known and phi₀Is the initial value of the magnetic flux phi. In the context of the present invention, the integration interval preferably starts at the moment when the electronic control device 40 commands the opening of the electromagnetic actuator 30, i.e. the time t₂'.

The magnetic flux Φ can be calculated by a numerical calculation method implemented by the electronic control device 40 using equation 3.

The shorter the integration time interval dt, i.e. the shorter the integration step, the smaller the calculation error. This interval dt is, for example, proportional to the inverse of the clock frequency of the central processing unit of the electronic control device 40. According to some examples, the clock frequency of the apparatus 40 is 1 kHz.

To pass through to U_BOBAnd I_BOBIs integrated to calculate the flux phi and the inverse function x is used to be g (phi, I)_BOB) Determining the change in the position x of the movable core 34 requires determining the initial flux phi₀. Defining an estimate of the initial flux

The first method involves estimating the initial value of the position x (which is expressed as an estimate value)

) Using a known response surface phi ═ f (x, I)_BOB) To determine

The value of (c). The estimated value

For example, by knownCoil inductance L_BOBTo calculate the coil current I_BOBIs measured. Thus, the

As a variation, where the core 34 is adjacent in the closed position, the estimate may be estimated from the geometry of the actuator 30

However, this determination of the position estimate

The first method of (a) is relatively approximate and does not allow, among other things, to take into account the variability of the size of the magnetic gap. For example, contamination of the fit or clearance of the surfaces may result in this estimated position being considered closed

Which results in an initial flux

Errors in the estimation, resulting in errors in the reconstruction of the position x during the off phase.

The second method, known as self-correction, is based on the fact that: if the coil current I_BOBHigher than locked rotor current I_SThe movable core 34 remains stationary in the closed position in the opening phase P4, i.e. at the stalling time t₂"before, assume that the core 34 remains stationary in the closed position.

In other words, at t₂' and t₂"at any time t between, as long as the coil current I_BOBGreater than locked rotor current I_SWhen the magnetic flux phi is calculated using equation 3 and the inverse function x is equal to g (phi, I)_BOB) From which the position x at time t is derived, if the calculated position is not constant, in other words x (t) ≠ x (t)₂') initial flux then

Is estimatedThere is an error in the meter. Then, the magnetic flux phi at time t is compensated to correct the error, the compensation resulting in re-estimating the initial flux

Correcting the flux phi a plurality of times in a plurality of successive calculations, and assuming that the time t is included at t₂' and t₂"until the initial flux

Estimated value of (c) and actual flux phi₀And (6) converging. As a result of the automatic correction method, the initial flux φ₀The error in (b) is accurately compensated.

Therefore, when the coil current I_BOBReduced to below locked-rotor current I_SAnd the core 34 begins to move, accurate knowledge of the magnetic flux phi allows the position x to be accurately calculated.

Fig. 6 shows a diagram 68 illustrating an embodiment of the self-correction method. In fig. 68, a curve 70 shows the dependence on the coil current I_BOBThe magnetic flux phi calculated by self-correction multiplied by the number of turns of the coil 32, the initial position x set and the initial flux phi

The estimate of (b) is erroneous. In an example, the estimated initial position

And the initial flux phi₀Is the magnetic flux corresponding to the position x +0.02 mm. It can be seen that there is a divergence of the magnetic flux phi with respect to the characteristic corresponding to the set position x, resulting in a series of self-corrections until the estimated flux and the actual flux phi converge. The convergence of the estimated flux results in a stable calculated position x, which corresponds to the actual position x.

The curve 72 shows the magnetic flux φ calculated by self-correction, the initial magnetic flux φ₀There is no error. In an example, the estimated initial position

Initial magnetic flux

The magnetic flux corresponding to this position x +0.02 mm. The calculated flux does follow the characteristics of the set position and does not require correction.

Fig. 7 shows a graph 74 illustrating the effect of the self-correction method on the position x determination. The curve 76 (dashed line) shows the variation of the position x, which is measured directly using a sensor of the position of the movable core 34, for comparison with the results of the method described above. It will be appreciated that in practice the contactor 1 is typically free of such position sensors.

In the initial phase P74, the measurement position x is kept constant. In stage P75, after the initial stage P74, the core 34 moves from its closed position to its open position, and the position x changes. In phase P76, after phase P75, the core 34 is in its stable open position, and the position x is again constant.

Curve 78 (bold dashed line) shows the change in position x, calculated using the method described above without self-correction. Estimated initial flux

Is erroneous and not corrected.

The curve 80 shows the position x variation of the closing phase, calculated using the method described above, with self-correction, the initial conditions being the same as those of the calculation of the curve 78. Estimated initial flux

Is erroneous but corrected.

In the initial phase P74, the position x is kept constant. The curve 80 includes a step-like variation 81 resulting from the execution of the self-calibration routine. Furthermore, despite the initial flux φ₀There is uncertainty, but curve 80 is connected to curve 76. As a result, in phases P75 and P76, curve 80 corresponds better to curve 76 than curve 78, which demonstrates the positive effect of the self-correction method. Without the need for position sensors to be mounted to reliably determine the presence of a closed stepThe change in position x as a function of time in segment P2. Advantageously, the self-correction method is implemented in all cases.

The non-linear nature of ferromagnetic materials means that the magnetic flux phi is less sensitive to gap variations when the magnetic circuit, and in particular the coil 32, is saturated. This effect is illustrated in fig. 8, which shows a graph 82 showing an air gap per millimeter

As a function of the magnetic flux phi, which is equal to the coil current I_BOBMultiplied by the number of turns N. Thus, the coil current I_BOBThe higher the sensitivity of the magnetic flux phi as a function of the gap, or in other words as a function of the position x, is lower.

For this purpose, after receiving an opening command, when the coil current I_BOBAs high as possible, the electronic control device 40 commands the opening of the electromagnetic actuator 30, i.e. higher than or equal to the high threshold I₂Is preferably above the high threshold I₂More preferably above the high threshold I₂98% of the total. This allows the magnetic circuit to saturate and provides more time to implement the self-calibration method.

An operation example of a method for estimating the characteristics of the contactor 1 according to a preferred embodiment will now be described with reference to fig. 9. However, as a variant, the steps of the method may be performed in a different order. Some steps may be omitted. In other embodiments, the described examples do not prevent other steps from being performed in conjunction with and/or sequentially to the described steps.

In step 100, the method is initialized when the contactor 1 is initially in a stable closed state, for example in the hold phase P3. The electronic control device 40 is waiting for a command to open the contactor 1.

Next, in step 102, the electronic control device 40 receives a command to open the contactor 1. Time t of receiving a disconnect command₂Is the start of the disconnection phase P4.

Next, in step 104, the electronic control device 40 commands the electromagnetic actuator 30 to open at time t 2'. Here, the opening command includes dropping a command voltage across the terminals of the coil 32 to zero.

Preferably, when the coil current I_BOBHigher than or equal to a high threshold I₂Preferably higher than 95%, more preferably higher than 98%, the electronic control means 40 command the opening of the electromagnetic actuator 30.

At holding stage P3 until time t₂', coil voltage U_BOBPeriodically varying at a frequency F3, where F3 equals 100 Hz; in other words, the periodic variation of the coil voltage defines a period equal to 1/F3, i.e. here 10 ms.

Advantageously, the electronic control device 40 commands the opening of the electromagnetic actuator 30 at the end of a predetermined duration at the latest after receiving the opening command. According to some examples, the predetermined duration is equal to the coil voltage U_BOBI.e. here 10 ms.

Next, in step 106, the electronic control device 40 measures and stores the coil current I_BOBAnd coil voltage U_BOBFor example until the contactor 1 reaches its open position, or indeed within a predetermined length of storage time, which is stored in the electronic control unit. The length of time of this storage is for example equal to 5 periods of 50Hz supply current, i.e. 100 ms.

Next, the method includes a step 112 of calculating and storing the magnetic flux φ flowing through the coil 32.

Step 112 includes a substep 110 in which a current I is passed through the coil_BOBAnd coil voltage U_BOBAnd the coil resistance R stored in advance in the electronic control device 40_BOBAnd a coil inductance L_BOBThe magnetic flux phi is calculated by integrating the values of (c).

Step 112 advantageously comprises an initial self-correction sub-step 108, which, after sub-step 110, comprises, assuming a coil current I_BOBAbove a low threshold I₁And the core 34 is still in the closed position, the estimated magnetic flux phi₀By taking into account the initial flux phi calculated in the self-correction sub-step 108₀Is advanced for the magnetic flux phi in sub-step 110And (4) calculating line integrals.

According to some examples, self-correcting sub-step 108 is from time t₂' last until locked-rotor time t₂And sub-step 110 at time t₂"start.

Next, the method includes step 114, step 114 including basing the magnetic flux φ and the coil current I on one hand_BOBOn the other hand, the position x of the contactor 1 is evaluated and stored according to the characteristics of a data table of the electromagnetic actuator 30, stored in advance in the electronic control device 40 and defining the position x of the core 34, the magnetic flux phi and the coil current I_BOBA bijective relationship between.

Fig. 10 shows a diagram illustrating the position x and the coil voltage U in the switch-off phase P4_BOBGraph 84 of the variation of (a). Time t₄Is defined as the time during which the movable core 34 is stable in its open position. The stroke Δ x of the movable core 34 is also defined to be equal to the time t₂' and t₄The difference between the positions x when in the open position and the closed position.

The release time Δ t is also defined to be equal to the time t at which the electronic control device 40 commands the opening of the electromagnetic actuator 30₂' and the time t at which the electromagnetic actuator 30 is stably in its open position₄The time elapsed in between.

Knowing the position x allows various conclusions to be drawn about the state of the contactor 1.

According to a first example, the method is configured to compare the travel Δ x of the movable core 34 with a reference value stored in the electronic control device 40 in order to detect potential defects of mechanical nature.

According to another example, the method is configured to verify the absence of friction or mechanical origin blocking by comparing the release time Δ t with a reference time stored in the electronic control device 40.

In step 116 of the method, the distribution of the moving speed v of the contactor 1 and the distribution of the acceleration a of the contactor 1 are calculated by differentiation with respect to time of the value of the position x stored in step 114. The curves of the velocity v and the acceleration a are stored in the electronic control device 40. By extension, the distribution of the velocity v and the acceleration a of the contactor 1 is also the distribution of the velocity v and the acceleration a of the electromagnetic actuator 30 or the movable core 34.

Next, in step 118, the electronic control device 40 is configured to calculate a speed, called "separation" speed, which is equal to the speed v of the contactor 1 when the position x of the contactor 1 has reached a position called "maximum overtravel" position and denoted Emax, corresponding to the movement of the core 34 from the closed position to the open position. In practice, this movement depends on the geometry of the actuator 30 and is generally comprised between 0.5mm and 3mm, and is for example equal to 2 mm. Preferably, the electronic control means 40 are configured to generate an alarm if the separation speed is lower than a threshold value pre-stored in the electronic control means 40.

Fig. 11 shows a graph 86, which shows three

speed curves

86A, 86B and 86C in the opening phase P4, corresponding to the speed v curves of three cores 34 of a contactor 1 of the same model but with different wear states: new, slightly worn and worn, respectively.

The separation speeds of the core 34 of the new, slightly worn and worn contactor 1 are defined as separation speeds V1, V2 and V3, respectively.

By comparing the separation speeds V1, V2 and V3, the effect of contactor wear on the separation speed can be observed. The more the contactor 1 is worn, the lower the separation speed. A minimum separation speed threshold can thus be defined below which the electronic control device 40 generates an alarm to signal to the user that maintenance must be scheduled.

For the contactor 1 in a good condition, from the locked-rotor time t₂"initially, the magnetic force is never higher than the force due to the return member 36, which results in a strict increase in the velocity v until the core 34 reaches the abutment open position at the end of its stroke. In the event of wear of the contactor 1, in particular when the contact pads 29 are worn and the surface of the contact pads 29 is damaged, in the holding phase P3, a micro-weld is formed between the pads 29 of the movable and fixed

contacts

24, 28. When the contactor 1 opens, the breaking of the micro-welds slows down the movement of the movable core 34 and when the core 34 reaches the open positionBefore the abutment, the speed v contains a descending section.

Fig. 12 shows a graph 88 showing three

speed curves

86A, 86B and 86C in the opening phase, corresponding to the speed v of the core 34 of three contactors 1 of the same model but with different micro-welding conditions: respectively healthy product, light mu welding and strong mu welding. The three

speed profiles

88A, 88B and 88C are synchronized, i.e. the movement is at the same time t₈₈And starting. In other words, until time t₈₈The speed is kept at 0.

The curve 88A corresponding to the healthy contactor 1 monotonically increases from time t88 to a peak 90 at which the core 34 reaches the abutment point.

Curve 88B corresponds to contactor 1 with a light weld, with a peak 94 at the point where the core 34 reaches abutment. However, curve 88B is not from time t₈₈Monotonically increases to peak 94, but at time t₈₈And peak 94, a decreasing segment followed by another increasing segment. The junction between the decreasing segment and the increasing segment has a horizontal tangent and defines a local minimum 92 of the curve 88B. In other words, the velocity profile 88B includes the time t at which the movement begins₈₈A local minimum 92 between the time at which the core 34 reaches the peak 94 at the abutment.

Curve 88C corresponds to contactor 1 with a strong micro-weld, at time t when the movement starts₈₈And the time at which the core 34 reaches the abutment peak 98, the local minimum 96 is contained, the local minimum 96 being more pronounced than the local minimum 92 of the curve 88B. In other words, the stronger the micro-welding, at time t when the movement of the core 34 starts₈₈And the moment at which the core 34 reaches the abutment of the open position, the more pronounced the local minimum of the velocity v.

More generally, the diagnostic method according to the invention enables to determine precisely the curve of the position x of the movable core 34 as a function of time and the curves of the speed v and of the acceleration a, these curves being derived from the curve of the position x. This information can be combined in various ways to monitor wear of certain parts of the contactor 1, such as the contact pads 29, or indeed the mechanism of the electromagnetic actuator 30.

In the example shown, the electronic control device 40 performs the function of controlling the shut-off device 30 and the function of implementing the diagnostic method according to the invention.

As a variant (not shown), the diagnostic method is implemented by a specific electronic device, which is added to the existing contactor during maintenance operations. Such a special device only requires the coil current I in order to implement the diagnostic method according to the invention_BOBAnd coil voltage U_BOBThe measurement of (2).

According to another variant, when the contactor 1 comprises an electronic control device 40 not configured to implement the diagnostic method according to the invention, the electronic control device 40 of the contactor 1 can be configured if sensors of the coil current and of the coil voltage are present, so as to be able to implement the diagnostic method according to the invention, for example by physically replacing the electronic control device 40 or, indeed, by changing the calculation code of the electronic control device 40, where appropriate.

The embodiments and variants mentioned above can be combined with each other to produce new embodiments of the invention.

Claims

1. A method for diagnosing an operating state of a switchgear device (1), the device (1) being configured to be coupled to an electrical conductor (20) and comprising:

-separable contacts (24, 28) associated with the electrical conductors and driven by an electromagnetic actuator (30), the electromagnetic actuator (30) comprising a coil (32) connected to an electronic control device (40), the control device being configured to apply a coil command voltage (U) across terminals of the coil_BOB)，

-a sensor (Rsh, 50) configured to measure a coil voltage (U)_BOB) And a coil current (I) flowing through the coil_BOB) The size of (a) is (b),

the method is characterized by comprising the following steps:

a) -receiving (102) a command to open a switching device, said switching device being initially in a closed state, the opening command being received by said electronic control means;

b) -commanding (104), by means of said electronic control device (40), the opening of said electromagnetic actuator (30) after receiving said opening command;

c) measuring and storing (106) a coil voltage (U) when the switching device (1) is switched to an off-state_BOB) And coil current (I)_BOB) A value of (d);

d) by comparing the stored values of the coil current and the coil voltage with the resistance (R) of the coil previously stored in the electronic control unit_BOB) And an inductance (L)_BOB) Calculating and storing (112) the value of the magnetic flux (phi) passing through the coil (32);

e) based on the stored magnetic flux (phi) and the coil current (I)_BOB) Evaluating and storing (114) the position (x) of the core (34) of the electromagnetic actuator (30) according to the characteristics of a data table of the electromagnetic actuator, which is stored in advance in the electronic control device (40) and defines the position (x) of the core (34), the magnetic flux (phi) and the coil current (I)_BOB) A bijective relationship between.

2. A method as claimed in claim 1, wherein the step (112) of calculating the magnetic flux (Φ) comprises an initial sub-step (108), called self-correction sub-step, followed by a calculation sub-step (110), the self-correction sub-step comprising: at the coil current (I)_BOB) Above low threshold (I)₁) In the case of (2), an initial value of the magnetic flux (phi) is evaluated and stored, this value being called "initial flux" (phi)₀) So that when the coil current (I)_BOB) Down to the locked-rotor current (I)_S) When following, in a calculation phase (110), the initial flux (phi) is taken into account by a calculation of the integral of the magnetic flux (phi)₀) The low threshold itself being strictly higher than the current (I) known as the "locked rotor" current_S) Below which the movable core (34) is repelled by a return member (36) of the electromagnetic actuator (30) to an open position.

3. Method according to claim 2, wherein the electronic control device (40) is configured to cause a coil voltage (U) when the switching device (1) is in a closed state_BOB) Is varied so that the coil current (I)_BOB) At low threshold (I)₁) And a high threshold (I) strictly higher than said low threshold₂) And wherein, upon receipt of said turn-off command, the coil current (I) is measured_BOB) Higher than or equal to the high threshold (I)₂) Preferably higher than 95%, more preferably higher than 98%, the electronic control means command the opening of the electromagnetic actuator (30).

4. Method according to claim 3, wherein the coil voltage (U) is caused to be_BOB) Periodically varying, e.g. by chopping, coil current (I)_BOB) Also at the low and high thresholds (I)₁，I₂) And wherein, upon receipt of said opening command, said electronic control means (40) command, at the latest, the opening of said electromagnetic actuator (30) at the end of a predetermined duration following the receipt of the opening command, said predetermined duration being equal to said coil voltage (U)_BOB) One period of (a).

5. The method according to any one of the preceding claims, wherein the electronic control device (40) is configured to calculate a time, called "release" time (Δ t), equal to the time elapsed between the time at which the electronic control device commands the opening of the electromagnetic actuator (30) and the time at which the electromagnetic actuator reaches the open position.

6. The method according to any one of the preceding claims, wherein the method comprises the following step (116): by deriving the position (x) value of the switching device (1) with respect to time, stored in the electronic control means (40), a profile of the movement speed (v) of the switching device and a profile of the acceleration (a) of the switching device are calculated and the speed profile and the acceleration profile of the switching device are stored in the electronic control means (40).

7. Method according to claim 6, wherein it comprises a step (118) of calculating a value of speed, called "separating" speed (V1, V2, V3), equal to the speed (V) of movement of the core (34) when the core (34) is in a position called "maximum overtravel" position, corresponding to the movement of the core from its closed position to its open position, substantially equal to 2 mm.

8. The method according to claim 6 or 7, wherein the method comprises the following step (118): -detecting, in the opening phase of the switchgear (1), a local minimum (92, 96) of the speed (v) of the core (34) between the start of the movement of the core (34) and the moment at which the core (34) reaches the abutment of the open position.

9. An electrical switching apparatus (1) for implementing the diagnostic method according to any one of claims 1 to 8, the switching apparatus comprising:

-separable contacts (24, 28) movable between open and closed positions by an electromagnetic actuator (30), said electromagnetic actuator (30) comprising a coil (32) and a movable core (34) attached to said separable contacts, said switching apparatus having a structure that limits eddy current generation;

-an instruction circuit (51) for controlling the voltage across the terminals of the coil (32), said voltage being called "coil voltage" (U)_BOB) The command circuit comprises means, called "release" means (Dz), which can be selectively activated to drop the current through the coil (32), called "coil current" (I)_BOB) -the coil voltage and release means are activated or deactivated according to the state of said command circuit (51);

-sensors (Rsh, 50) for measuring coil current and coil voltage;

-electronic control means (40) configured to receive commands to open and close said switching device, to receive measurements of the coil current and of the coil voltage, and to control the state of said command circuit;

a) a command to open the switching device is received (102).

b) Commanding (104) the electromagnetic actuator (30) to open;

c) measuring and storing (106) the coil voltage (U)_BOB) And coil current (I)_BOB) A value of (d);

d) by means of stored values for the coil current and the coil voltage and the resistance (R) of the coil stored beforehand in the electronic control unit_BOB) And an inductance (L)_BOB) Calculating and storing (112) the value of the magnetic flux (phi) passing through the coil (32);

e) evaluating and storing (114) the position (x) of the core (34) according to a data table characteristic of the electromagnetic actuator (30), the data table being pre-stored in the electronic device and defining the position (x) of the core (34), the magnetic flux (phi) and the coil current (I)_BOB) A bijective relationship between.